Fast radio bursts in space causes a stir

By Alan Hale

For the Daily News

Posted:
07/11/2013 07:20:53 PM MDT

Many of us love a good mystery, whether it's a novel, an element in a favorite television program or movie, or a murder mystery production that this author has occasionally participated in as a result of his membership in the local acting troupe. Many of us enjoy the process of sifting through clues and applying our reasoning powers in an effort to solve the mystery scenario that is being presented to us.

Much of science, and almost all of our major scientific discoveries, have come about as a result of this process -- chasing down a mystery. As the late and noted science and science fiction writer Isaac Asimov reportedly once quipped, "The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka! I found it!' but 'That's funny ...'"

Certainly, this has been true for many astronomical discoveries. One rather notable recent example involves the so-called "gamma-ray bursts" -- brief but intense bursts of high-energy gamma-ray radiation that occur seemingly at random from all over the sky. Since our atmosphere blocks gamma-ray radiation from reaching the surface -- which is fortunate for us -- we were completely unaware of it until satellites specifically designed to detect gamma-rays were launched and placed into orbit. Once there, these satellites began detecting these bursts at a rate of approximately one per day.

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The origin and nature of these bursts remained a mystery for some time. It wasn't until they began being "caught in the act" by telescopes sensitive to visible light and other parts of the electromagnetic spectrum that we began to understand what was going on with these events.

Although we're still quite a ways from a complete understanding, at least some gamma-ray bursts appear to occur when two neutron stars -- very small but dense and massive remnants of large stars that have exploded as supernovae -- collide with each other, triggering bursts of radiation that are detectable from large distances across the universe.

At the opposite end of the electromagnetic spectrum from gamma-rays are the longer wavelength radio waves. These have generated some mysterious phenomena as well.

In the late 1960s, a British graduate student named Jocelyn Bell detected very short and regular pulses of radio waves that repeated very rapidly, coming from various locations around the sky. At first, these were whimsically dubbed "LGMs" (for "Little Green Men") since they superficially mimicked what one might expect from an alien transmission. But they were quickly more formally named "pulsars" (for "pulsating stars"). We now know that pulsars are due to radio waves being emitted by rapidly rotating neutron stars.

And now, we have another astronomical radio mystery on our hands. Once again, a British graduate student, Dan Thornton of the University of Manchester, has made a discovery.

While sifting through some high-time resolution data taken with the Parkes Radio Telescope in Australia, Thornton detected the signals of four extremely short, but very intense, bursts of radio waves coming from apparently random locations in the sky. One of these came from the southeast of the prominent constellation Sagittarius (which currently takes center stage in our southern sky around midnight), and the other three from the vicinity of the constellations Aquarius and Pisces (which are now visible before dawn).

Each of these four events -- which have now been dubbed FRBs (for "fast radio bursts") -- lasted just a few milliseconds and exhibited the property that the lower frequencies arrived somewhat later than the higher frequencies, meaning that they have traveled immense distances across the universe and interacted with the very sparse gas that lies in extragalactic space. Calculations suggest that these FRBs took place 5 billion to 10 billion light-years away.

Now that the discovery of these FRBs has been announced, there has come to light reports of other similar events that have been recorded in the past, including another one recorded from Parkes in 2001. Although not noticed and reported until six years later, that was so intense that the processing software assumed that the event was artificial and deleted part of the data. Based upon the amount of sky that has been covered and the time scales that have been examined, Thornton and his colleagues estimate there could be as many as 10,000 FRBs going off every day all over the sky.

So, just what is causing these FRBs? No one really knows yet, although one idea that has been floated around suggests that these may be due to energetic flares on objects called "magnetars," i.e., neutron stars with extremely strong magnetic fields.

Regardless of whether this, or some other explanation, eventually turns out to be correct, we first have to begin catching these events "in the act" and observing them with other wavelengths. Trying to catch a phenomenon that occurs several hundred times faster than an eye blink, and doing so with enough frequency to make serious study of this phenomenon worthwhile, is not going to be easy.

But we really don't want our mysteries to be too easy, right?

Alan Hale is a professional astronomer who resides in Cloudcroft. He is involved in various space-related research and educational activities throughout New Mexico and elsewhere. His website is earthriseinstitute.org.